The invention refers to an improvement in the machines for paper manufacture and, in particular, but not exclusively, to machines for rewinding small rolls from big rolls.
In the paper-making industry, and particularly in the manufacture of kitchen towels in roll form and toilet paper in roll form, the extremely large rolls of webs of paper which are made on a paper machine must be converted to the smaller size roll, and this is usually done "off machine" on a re-winding machine which operates at high speed and produces a plurality of the smaller rolls wound on a cardboard tube or core. Such a rewinder generally comprises a continuously rotating cylinder, which advances and controls the web material, as well as cuts the web when a log or roll of paper wound on a core has been completed and when the winding on another core must begin.
When the cutting of the web takes place across the cutting arc of the advancement cylinder, it is necessary to temporarily retain the ends of the web at least in the zone adjacent to the cut. This must be carefully timed in order to control the web during the advancement and to release it in time (upon the completion of the last turn of a previous roll or log) at the beginning of the winding of a new roll or log on another core. At this instant, it is necessary to release the paper end so as not to interfere with the winding of the new roll.
Pneumatic-operated suction systems to retain the light web of paper are well known. It is necessary to control the suction with precise timing during a pre-determined phase of the rotation cycle of the cylinder, when the core replacement and a new winding is to take place. The prior means cause significant construction difficulties and, in particular, significant difficulties in the maintenance and in the changes on the cylinder, with significant lost production time and complications in the machine adjustment both during the removal of the cylinder and during the re-assembly of same cylinder after the changing.